To fix the one you have.. there isn't enough money. Could be a seal etc....my preference since trans building takes me too much time is to swap one in. car-part is listing a few around the 120-140K mile range for $300-$400, add on labor and fluid and it could be done in a day. Depending on how long you plan to keep the car, I'd consider suggesting a PCS and 4th hub shaft get put in before the trans goes into the car. That way you know the two most common issues are fixed.